Abstract
We investigate the formation of multiple-core-hole states of molecular nitrogen interacting with a free-electron laser pulse. In previous work, we obtained bound and continuum molecular orbitals in the single-center expansion scheme and used these orbitals to calculate photo-ionization and auger decay rates. We extend our formulation to track the proportion of the population that accesses single-site versus two-site double-core-hole (TSDCH) states, before the formation of the final atomic ions. We investigate the pulse parameters that favor the formation of the single-site and TSDCH as well as triple-core-hole states for 525 and 1100 eV photons.
Highlights
The production of free-electron lasers (FELs) [1] with x-ray photon energies has led to new methods of investigating atoms and molecules [2, 3], and of imaging biomolecules [4,5,6,7]
Using the molecular and atomic auger and photo-ionization yields, we plot in figures 1(a), (b) the electron spectra generated by an FEL pulse with 525 eV (1100 eV) photon energy, with a full width at half maximum (FWHM) pulse duration of 4 fs and with a peak intensity of 1017 W cm−2 (1018 W cm−2)
And (c), we find that for short duration of 4 fs FWHM and high intensity FEL pulses, 49% and 56% of all pathways contributing to all final atomic ion yields are pathways that have accessed two-site double-core-hole states (TSDCH) and triple-core-hole states (TCH) molecular states
Summary
The production of free-electron lasers (FELs) [1] with x-ray photon energies has led to new methods of investigating atoms and molecules [2, 3], and of imaging biomolecules [4,5,6,7]. The x-ray energy allows the single-photon ionization of core electrons and the creation of core-hole states. These core-hole states have lifetimes of a few femtoseconds. These states decay via auger processes, in which the core hole is filled by a less-bound electron and the released energy allows another less-bound electron to escape. Several studies have addressed double-core-hole (DCH) states of molecules, as they are of particular interest for chemical analysis [8, 9] The energy of these states is highly dependent on the chemical environment, making them an appropriate basis for spectroscopic measurements. DCH states are either single-site double-core-hole states (SSDCH) with the core holes on one atomic site or two-site double-core-hole states (TSDCH) with
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